1. Field of the Invention
The present invention relates to airborne radars or radars on board satellites.
When an airborne radar works in imaging mode (SAR or synthetic aperture radar), the fidelity of the image to reality depends on the precision with which the modulus of the speed of the radar carrier vehicle is known. Any lack of precision in the knowledge of the modulus of the speed of the radar results in a deformation of the image which adversely affects the measurements of distance made in this image. To obtain precise distance measurements on a radar image; it is therefore necessary to know the modulus of the speed of movement of the carrier with extremely great precision.
2. Description of the Prior Art
In the prior art, it is habitual to determine the speed of movement of the carrier, either by means of the radar itself, which then works in a specific mode of measurement of the speed vector of the carrier, this mode being different from the imaging mode and making use of the locking of the radar to its carrier, or by means of a distinct device of the radar such as a satellite navigation system (GPS) or, if its precision allows it, the inertial guidance unit.
It is proposed here to determine the modulus of the speed of movement of the carrier of a radar by means of the radar by itself, without bringing into play the locking of this radar with respect to its carrier, and independently of the drift of the carrier due to any cross-wind, in order to improve the precision of the measurement and avoid the need to use a system other than the radar itself.